U.S. patent number 8,334,748 [Application Number 13/357,671] was granted by the patent office on 2012-12-18 for method for manufacturing ceramic electronic component and ceramic electronic component.
This patent grant is currently assigned to Murata Manufacturing Co., Ltd.. Invention is credited to Toshiyuki Iwanaga, Teruyo Katayama, Kenichi Kawasaki, Akihiro Motoki, Makoto Ogawa, Syunsuke Takeuchi.
United States Patent |
8,334,748 |
Takeuchi , et al. |
December 18, 2012 |
Method for manufacturing ceramic electronic component and ceramic
electronic component
Abstract
A method for manufacturing a ceramic electronic component
includes the steps of preparing a ceramic body including a
plurality of first internal electrodes and a plurality of second
internal electrodes, processing the ceramic body to an internal
electrode exposure rate of about 102% to about 153%, and plating
the processed ceramic body to form a plated layer thereon.
Inventors: |
Takeuchi; Syunsuke (Nagaokakyo,
JP), Katayama; Teruyo (Nagaokakyo, JP),
Iwanaga; Toshiyuki (Nagaokakyo, JP), Motoki;
Akihiro (Nagaokakyo, JP), Ogawa; Makoto
(Nagaokakyo, JP), Kawasaki; Kenichi (Nagaokakyo,
JP) |
Assignee: |
Murata Manufacturing Co., Ltd.
(Kyoto, JP)
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Family
ID: |
46544044 |
Appl.
No.: |
13/357,671 |
Filed: |
January 25, 2012 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20120188683 A1 |
Jul 26, 2012 |
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Foreign Application Priority Data
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Jan 26, 2011 [JP] |
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2011-014225 |
Dec 28, 2011 [JP] |
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2011-288154 |
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Current U.S.
Class: |
336/200 |
Current CPC
Class: |
H01G
4/232 (20130101); H01C 7/008 (20130101); H01G
4/30 (20130101); H01G 4/012 (20130101); H01C
1/148 (20130101); H01C 7/18 (20130101) |
Current International
Class: |
H01F
5/00 (20060101) |
Field of
Search: |
;336/65,83,192,200,232
;361/321 ;29/602.1,609,825,842,846,851 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2007-036003 |
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Feb 2007 |
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JP |
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2007/049456 |
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May 2007 |
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WO |
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2007/105395 |
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Sep 2007 |
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WO |
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Other References
Kunishi et al., "Laminated Electronic Component and Method for
Manufacturing the Same", U.S. Appl. No. 12/030,282, filed Feb. 13,
2008. cited by other .
Kunishi et al., "Laminated Electronic Component and Method for
Manufacturing the Same", U.S. Appl. No. 12/030,360, filed Feb. 13,
2008. cited by other .
Tani, "Multilayer Electronic Component and Method for Manufacturing
the Same", U.S. Appl. No. 12/481,690, filed Jun. 10, 2009. cited by
other .
Ito et al., "Laminated Ceramic Electronic Component", U.S. Appl.
No. 12/489,631, filed Jun. 23, 2009. cited by other .
Sasabayashi, "Multilayer Ceramic Electronic Component", U.S. Appl.
No. 12/765,965, filed Apr. 23, 2010. cited by other .
Sasabayashi et al., "Electronic Component", U.S. Appl. No.
13/092,996, filed Apr. 25, 2010. cited by other.
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Primary Examiner: Nguyen; Tuyen
Attorney, Agent or Firm: Keating & Bennett, LLP
Claims
What is claimed is:
1. A method for manufacturing a ceramic electronic component
including a substantially rectangular ceramic body including six
surfaces including a pair of surfaces extending in a length
direction and a width direction perpendicular to the length
direction, a pair of surfaces extending in the length direction and
a thickness direction perpendicular to the length direction and the
width direction, and a pair of surfaces extending in the width
direction and the thickness direction, a plurality of first
internal electrodes disposed in the ceramic body and extending to
at least one of the six surfaces of the ceramic body, a plurality
of second internal electrodes disposed opposite to the first
internal electrodes in the ceramic body and extending to at least
one of the six surfaces of the ceramic body, a first external
electrode disposed on the ceramic body and connected to the first
internal electrodes, and a second external electrode disposed on
the ceramic body and connected to the second internal electrodes,
the first and second internal electrodes including opposing
portions disposed opposite to each other and lead portions that are
not disposed opposite to each other, the lead portions being
connected to the opposing portions and extending to the surfaces of
the ceramic body, the first and second external electrodes each
comprising at least one plated layer formed by plating on the
ceramic body, the method comprising the steps of: preparing the
ceramic body including the plurality of first and second internal
electrodes; processing the ceramic body to a first internal
electrode exposure rate of about 102% to about 153% and a second
internal electrode exposure rate of about 102% to about 153%,
wherein the first internal electrode exposure rate is a proportion
of the exposure rate of the lead portions of the first internal
electrodes in the surface to which the first internal electrodes
extend to the exposure rate of the lead portions of the first
internal electrodes in a cross-section of the ceramic body parallel
or substantially parallel to the surface to which the first
internal electrodes extend, and the second internal electrode
exposure rate is a proportion of the exposure rate of the lead
portions of the second internal electrodes in the surface to which
the second internal electrodes extend to the exposure rate of the
lead portions of the second internal electrodes in a cross-section
of the ceramic body parallel or substantially parallel to the
surface to which the second internal electrodes extend; and plating
the processed ceramic body to form the at least one plated layer
thereon.
2. The method for manufacturing the ceramic electronic component
according to claim 1, wherein the pair of surfaces of the ceramic
body extending in the length direction and the width direction are
first and second main surfaces, the pair of surfaces of the ceramic
body extending in the length direction and the thickness direction
are first and second side surfaces, and the pair of surfaces of the
ceramic body extending in the width direction and the thickness
direction are first and second end surfaces; the opposing portions
of the first internal electrodes are arranged in the thickness
direction in the ceramic body; the lead portions of the first
internal electrodes extend to the first end surface; the opposing
portions of the second internal electrodes are disposed between the
first internal electrodes adjacent in the thickness direction in
the ceramic body; and the lead portions of the second internal
electrodes extend to the second end surface.
3. The method for manufacturing the ceramic electronic component
according to claim 1, wherein the pair of surfaces of the ceramic
body extending in the length direction and the width direction are
first and second main surfaces, the pair of surfaces of the ceramic
body extending in the length direction and the thickness direction
are first and second side surfaces, and the pair of surfaces of the
ceramic body extending in the width direction and the thickness
direction are first and second end surfaces; the opposing portions
of the first internal electrodes being arranged in the width
direction in the ceramic body; the lead portions of the first
internal electrodes extend to at least one of the first and second
main surfaces; the opposing portions of the second internal
electrodes are disposed between the first internal electrodes
adjacent in the width direction in the ceramic body; and the lead
portions of the second internal electrodes extend to at least one
of the first and second main surfaces.
4. The method for manufacturing the ceramic electronic component
according to claim 1, wherein the ceramic body is polished by
barrel polishing in the processing step.
5. The method for manufacturing the ceramic electronic component
according to claim 1, wherein the at least one plated layer is
formed in the plating step by placing the processed ceramic body
and conductive media balls in a plating bath and stirring the
plating bath.
6. A ceramic electronic component comprising: a substantially
rectangular ceramic body including six surfaces including a pair of
surfaces extending in a length direction and a width direction
perpendicular to the length direction, a pair of surfaces extending
in the length direction and a thickness direction perpendicular to
the length direction and the width direction, and a pair of
surfaces extending in the width direction and the thickness
direction; a plurality of first internal electrodes disposed in the
ceramic body and extending to at least one of the six surfaces of
the ceramic body; a plurality of second internal electrodes
disposed opposite to the first internal electrodes in the ceramic
body and extending to at least one of the six surfaces of the
ceramic body; a first external electrode disposed on the ceramic
body and connected to the first internal electrodes; and a second
external electrode disposed on the ceramic body and connected to
the second internal electrodes; wherein the first and second
internal electrodes include opposing portions disposed opposite to
each other and lead portions that are not disposed opposite to each
other, the lead portions being connected to the opposing portions
and extending to the surfaces of the ceramic body; the first and
second external electrodes each including at least one plated layer
formed by plating on the ceramic body; the ceramic electronic
component having a first internal electrode exposure rate of about
102% to about 153% and a second internal electrode exposure rate of
about 102% to about 153%, wherein the first internal electrode
exposure rate is a proportion of the exposure rate of the lead
portions of the first internal electrodes in the surface to which
the first internal electrodes extend to the exposure rate of the
lead portions of the first internal electrodes in a cross-section
of the ceramic body parallel or substantially parallel to the
surface to which the first internal electrodes extend, and the
second internal electrode exposure rate is a proportion of the
exposure rate of the lead portions of the second internal
electrodes in the surface to which the second internal electrodes
extend to the exposure rate of the lead portions of the second
internal electrodes in a cross-section of the ceramic body parallel
or substantially parallel to the surface to which the second
internal electrodes extend.
7. The ceramic electronic component according to claim 6, wherein
the pair of surfaces of the ceramic body extending in the length
direction and the width direction are first and second main
surfaces, the pair of surfaces of the ceramic body extending in the
length direction and the thickness direction are first and second
side surfaces, and the pair of surfaces of the ceramic body
extending in the width direction and the thickness direction are
first and second end surfaces; the opposing portions of the first
internal electrodes are arranged in the thickness direction in the
ceramic body; the lead portions of the first internal electrodes
extend to the first end surface; the opposing portions of the
second internal electrodes are disposed between the first internal
electrodes adjacent in the thickness direction in the ceramic body;
and the lead portions of the second internal electrodes extend to
the second end surface.
8. The method for manufacturing the ceramic electronic component
according to claim 6, wherein the pair of surfaces of the ceramic
body extending in the length direction and the width direction are
first and second main surfaces, the pair of surfaces of the ceramic
body extending in the length direction and the thickness direction
are first and second side surfaces, and the pair of surfaces of the
ceramic body extending in the width direction and the thickness
direction are first and second end surfaces; the opposing portions
of the first internal electrodes are arranged in the width
direction in the ceramic body; the lead portions of the first
internal electrodes extend to at least one of the first and second
main surfaces; the opposing portions of the second internal
electrodes are disposed between the first internal electrodes
adjacent in the width direction in the ceramic body; and the lead
portions of the second internal electrodes extend to at least one
of the first and second main surfaces.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods for manufacturing ceramic
electronic components and to ceramic electronic components.
2. Description of the Related Art
Ceramic electronic components such as monolithic ceramic capacitors
have been extensively used in the related art. An example is
disclosed in International Publication No. WO2007/049456 A1. A
multilayer ceramic electronic component according to this
publication includes a rectangular ceramic body, first and second
internal electrodes, and first and second external electrodes. The
first and second internal electrodes are disposed opposite to each
other in the thickness direction in the ceramic body. The first
internal electrodes extend to one of the end surfaces of the
ceramic body. The second external electrodes extend to the other
end surface of the ceramic body. The first external electrode is
formed on one of the end surfaces of the ceramic body and is
electrically connected to the first internal electrodes. The second
external electrode is formed on the other end surfaces of the
ceramic body and is electrically connected to the second internal
electrodes.
The above publication also discloses a method for manufacturing the
multilayer ceramic electronic component by forming the first and
second external electrodes on the end surfaces of a ceramic body
including the first and second internal electrodes by plating.
The method according to the above publication, however, may
inappropriately form the first and second external electrodes.
SUMMARY OF THE INVENTION
Accordingly, preferred embodiments of the present invention provide
a method by which a ceramic electronic component can be
appropriately manufactured so as to include a substantially
rectangular ceramic body, internal electrodes extending to surfaces
of the ceramic body, and external electrodes electrically connected
to the internal electrodes and formed of a plated material.
A preferred embodiment of the present invention provides a method
for manufacturing a ceramic electronic component including a
substantially rectangular ceramic body, a plurality of first
internal electrodes, a plurality of second internal electrodes, a
first external electrode, and a second external electrode. The
ceramic body includes six surfaces including a pair of surfaces
extending in a length direction and a width direction perpendicular
to the length direction, a pair of surfaces extending in the length
direction and a thickness direction perpendicular to the length
direction and the width direction, and a pair of surfaces extending
in the width direction and the thickness direction. The first
internal electrodes are disposed in the ceramic body and extend to
at least one of the six surfaces of the ceramic body. The second
internal electrodes are disposed opposite to the first internal
electrodes in the ceramic body and extend to at least one of the
six surfaces of the ceramic body. The first external electrode is
disposed on the ceramic body and is connected to the first internal
electrodes. The second external electrode is disposed on the
ceramic body and is connected to the second internal electrodes.
The first and second internal electrodes include opposing portions
disposed opposite to each other and lead portions that are not
disposed opposite to each other. The lead portions are connected to
the opposing portions and extend to the surfaces of the ceramic
body. The first and second external electrodes each include a
plated layer formed by plating on the ceramic body. The method
includes the steps of preparing a ceramic body including the first
and second internal electrodes, processing the ceramic body to a
first internal electrode exposure rate of, for example, about 102%
to about 153% and a second internal electrode exposure rate of
about 102% to about 153%, and plating the processed ceramic body to
form the plated layer thereon. The first internal electrode
exposure rate is the proportion of the exposure rate of the lead
portions of the first internal electrodes in the surface to which
the first internal electrodes extend to the exposure rate of the
lead portions of the first internal electrodes in a cross-section
of the ceramic body parallel or substantially parallel to the
surface to which the first internal electrodes extend ((exposure
rate of lead portions of first internal electrodes in the surface
to which first internal electrodes extend)/(exposure rate of lead
portions of first internal electrodes in cross-section of ceramic
body parallel or substantially parallel to the surface to which
first internal electrodes extend)). The second internal electrode
exposure rate is the proportion of the exposure rate of the lead
portions of the second internal electrodes in the surface to which
the second internal electrodes extend to the exposure rate of the
lead portions of the second internal electrodes in a cross-section
of the ceramic body parallel or substantially parallel to the
surface to which the second internal electrodes extend ((exposure
rate of lead portions of second internal electrodes in the surface
to which second internal electrodes extend)/(exposure rate of lead
portions of second internal electrodes in cross-section of ceramic
body parallel or substantially parallel to the surface to which
second internal electrodes extend)).
In one particular preferred embodiment, the pair of surfaces of the
ceramic body extending in the length direction and the width
direction may be first and second main surfaces, the pair of
surfaces of the ceramic body extending in the length direction and
the thickness direction may be first and second side surfaces, and
the pair of surfaces of the ceramic body extending in the width
direction and the thickness direction may be first and second end
surfaces. The opposing portions of the first internal electrodes
may be arranged in the thickness direction in the ceramic body, and
the lead portions of the first internal electrodes may extend to
the first end surface. The opposing portions of the second internal
electrodes may be disposed between the first internal electrodes
adjacent in the thickness direction in the ceramic body, and the
lead portions of the second internal electrodes may extend to the
second end surface.
In one particular preferred embodiment, the pair of surfaces of the
ceramic body extending in the length direction and the width
direction may be first and second main surfaces, the pair of
surfaces of the ceramic body extending in the length direction and
the thickness direction may be first and second side surfaces, and
the pair of surfaces of the ceramic body extending in the width
direction and the thickness direction may be first and second end
surfaces. The opposing portions of the first internal electrodes
may be arranged in the width direction in the ceramic body, and the
lead portions of the first internal electrodes may extend to at
least one of the first and second main surfaces. The opposing
portions of the second internal electrodes may be disposed between
the first internal electrodes adjacent in the width direction in
the ceramic body, and the lead portions of the second internal
electrodes may extend to at least one of the first and second main
surfaces.
In one particular preferred embodiment, the ceramic body may be
polished by barreling in the processing step.
In one particular preferred embodiment, the plated layer may be
formed in the plating step by putting the processed ceramic body
and conductive media balls in a plating bath and stirring the
plating bath.
According to various preferred embodiments of the present
invention, a ceramic electronic component includes a substantially
rectangular ceramic body, a plurality of first internal electrodes,
a plurality of second internal electrodes, a first external
electrode, and a second external electrode. The ceramic body
includes six surfaces including a pair of surfaces extending in a
length direction and a width direction perpendicular or
substantially perpendicular to the length direction, a pair of
surfaces extending in the length direction and a thickness
direction perpendicular or substantially perpendicular to the
length direction and the width direction, and a pair of surfaces
extending in the width direction and the thickness direction. The
first internal electrodes are disposed in the ceramic body and
extend to at least one of the six surfaces of the ceramic body. The
second internal electrodes are disposed opposite to the first
internal electrodes in the ceramic body and extend to at least one
of the six surfaces of the ceramic body. The first external
electrode is disposed on the ceramic body and is connected to the
first internal electrodes. The second external electrode is
disposed on the ceramic body and is connected to the second
internal electrodes. The first and second internal electrodes
include opposing portions disposed opposite to each other and lead
portions that are not disposed opposite to each other. The lead
portions are connected to the opposing portions and extend to the
surfaces of the ceramic body. The first and second external
electrodes each include a plated layer formed by plating on the
ceramic body. The ceramic electronic component has a first internal
electrode exposure rate of, for example, about 102% to about 153%
and a second internal electrode exposure rate of about 102% to
about 153%. The first internal electrode exposure rate is the
proportion of the exposure rate of the lead portions of the first
internal electrodes in the surface to which the first internal
electrodes extend to the exposure rate of the lead portions of the
first internal electrodes in a cross-section of the ceramic body
parallel or substantially parallel to the surface to which the
first internal electrodes extend ((exposure rate of lead portions
of first internal electrodes in the surface to which first internal
electrodes extend)/(exposure rate of lead portions of first
internal electrodes in cross-section of ceramic body parallel or
substantially parallel to the surface to which first internal
electrodes extend)). The second internal electrode exposure rate is
the proportion of the exposure rate of the lead portions of the
second internal electrodes in the surface to which the second
internal electrodes extend to the exposure rate of the lead
portions of the second internal electrodes in a cross-section of
the ceramic body parallel or substantially parallel to the surface
to which the second internal electrodes extend ((exposure rate of
lead portions of second internal electrodes in the surface to which
second internal electrodes extend)/(exposure rate of lead portions
of second internal electrodes in cross-section of ceramic body
parallel or substantially parallel to the surface to which second
internal electrodes extend)).
In one particular preferred embodiment, the pair of surfaces of the
ceramic body extending in the length direction and the width
direction may be first and second main surfaces, the pair of
surfaces of the ceramic body extending in the length direction and
the thickness direction may be first and second side surfaces, and
the pair of surfaces of the ceramic body extending in the width
direction and the thickness direction may be first and second end
surfaces. The opposing portions of the first internal electrodes
may be arranged in the thickness direction in the ceramic body, and
the lead portions of the first internal electrodes may extend to
the first end surface. The opposing portions of the second internal
electrodes may be disposed between the first internal electrodes
adjacent in the thickness direction in the ceramic body, and the
lead portions of the second internal electrodes may extend to the
second end surface.
In one particular preferred embodiment, the pair of surfaces of the
ceramic body extending in the length direction and the width
direction may be first and second main surfaces, the pair of
surfaces of the ceramic body extending in the length direction and
the thickness direction may be first and second side surfaces, and
the pair of surfaces of the ceramic body extending in the width
direction and the thickness direction may be first and second end
surfaces. The opposing portions of the first internal electrodes
may be arranged in the width direction in the ceramic body, and the
lead portions of the first internal electrodes may extend to at
least one of the first and second main surfaces. The opposing
portions of the second internal electrodes may be disposed between
the first internal electrodes adjacent in the width direction in
the ceramic body, and the lead portions of the second internal
electrodes may extend to at least one of the first and second main
surfaces.
According to various preferred embodiments of the present
invention, a method is provided by which a ceramic electronic
component can be appropriately manufactured so as to include a
substantially rectangular ceramic body, internal electrodes
extending to surfaces of the ceramic body, and external electrodes
electrically connected to the internal electrodes and formed of a
plating.
The above and other elements, features, steps, characteristics and
advantages of the present invention will become more apparent from
the following detailed description of the preferred embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic perspective view of a ceramic electronic
component according to a first preferred embodiment of the present
invention.
FIG. 2 is a schematic sectional view taken along line II-II in FIG.
1.
FIG. 3 is a schematic sectional view taken along line III-III in
FIG. 1.
FIG. 4 is a schematic sectional view of a ceramic body before
barrel polishing in the first preferred embodiment of the present
invention.
FIG. 5 is a schematic sectional view showing in an enlarged view
the portion enclosed by circle V in FIG. 4.
FIG. 6 is a schematic sectional view showing in an enlarged view
the portion enclosed by circle VI in FIG. 4.
FIG. 7 is a schematic sectional view of a ceramic body after barrel
polishing in the first preferred embodiment of the present
invention.
FIG. 8 is a schematic sectional view illustrating a plating step in
the first preferred embodiment of the present invention.
FIG. 9 is a schematic sectional view illustrating a plating step in
a comparative example.
FIG. 10 is a schematic view illustrating regions for measurement of
internal electrode exposure rate.
FIG. 11 is a schematic view illustrating a step of stripping
external electrodes.
FIG. 12 is a schematic perspective view of a ceramic electronic
component according to a second preferred embodiment of the present
invention.
FIG. 13 is a schematic sectional view, taken in a length direction
L and a thickness direction T, of the ceramic electronic component
according to the second preferred embodiment of the present
invention.
FIG. 14 is a schematic sectional view, taken in the length
direction L and the thickness direction T, of the ceramic
electronic component according to the second preferred embodiment
of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Preferred Embodiment
A method for manufacturing a ceramic electronic component 1, shown
in FIG. 1, according to a first preferred embodiment of the present
invention will now be described. The following method for
manufacturing the ceramic electronic component 1 is merely
illustrative and should not be construed as limiting in any
way.
FIG. 1 is a schematic perspective view of the ceramic electronic
component 1 according to this preferred embodiment. FIG. 2 is a
schematic sectional view taken along line II-II in FIG. 1. FIG. 3
is a schematic sectional view taken along line III-III in FIG. 1.
The structure of the ceramic electronic component 1 manufactured in
this preferred embodiment will be described first with reference to
FIGS. 1 to 3.
As shown in FIGS. 1 to 3, the ceramic electronic component 1
includes a ceramic body 10. The ceramic body 10 preferably has a
substantially rectangular shape. The ceramic body 10 includes first
and second main surfaces 10a and 10b, first and second side
surfaces 10c and 10d, and first and second end surfaces 10e and
10f. The first and second main surfaces 10a and 10b extend in a
length direction L and a width direction W. The first and second
side surfaces 10c and 10d extend in the length direction L and a
thickness direction T. The first and second end surfaces 10e and
10f extend in the width direction W and the thickness direction T.
The length direction L and the width direction W are perpendicular
to each other. The thickness direction T is perpendicular to the
length direction L and the width direction W.
As used herein, the term "rectangular" encompasses rectangular
shapes with rounded corners or ridges. That is, the ceramic body 10
may have a substantially rectangular shape with at least partially
rounded corners or ridges.
In this preferred embodiment, the ceramic body 10 includes a
plurality of ceramic layers 15 stacked on top of each other in the
thickness direction T. The ceramic layers 15 preferably each have a
thickness of about 0.5 .mu.m to about 10 .mu.m, for example.
The ceramic body 10 is formed of an appropriate ceramic material.
The ceramic material for the ceramic body 10 is appropriately
selected based on, for example, the characteristics of the ceramic
electronic component 1.
If the ceramic electronic component 1 is, for example, a ceramic
capacitor, the ceramic body 10 may be formed of a material mainly
containing a dielectric ceramic. Examples of dielectric ceramics
include BaTiO.sub.3, CaTiO.sub.3, SrTiO.sub.3, and CaZrO.sub.3. The
ceramic body 10 may optionally contain a subcomponent such as a
manganese compound, an iron compound, a chromium compound, a cobalt
compound, or a nickel compound.
If the ceramic electronic component 1 is, for example, a ceramic
piezoelectric device, the ceramic body 10 may be formed of, for
example, a material mainly containing a piezoelectric ceramic.
Examples of piezoelectric ceramics include lead zirconate titanate
(PZT) based ceramics.
If the ceramic electronic component 1 is, for example, a
thermistor, the ceramic body 10 may be formed of, for example, a
semiconductor ceramic. Examples of semiconductor ceramics include
spinel ceramics.
If the ceramic electronic component 1 is, for example, an inductor,
the ceramic body 10 may be formed of a magnetic ceramic. Examples
of magnetic ceramics include ferrite ceramics.
The ceramic body 10 includes a plurality of first internal
electrodes 11 and a plurality of second internal electrodes 12. The
first and second internal electrodes 11 and 12 are arranged in the
thickness direction T in the ceramic body 10. The first and second
internal electrodes 11 and 12 are alternately arranged in the
thickness direction T. Accordingly, the second internal electrodes
12 are located between the first internal electrodes 11 adjacent in
the thickness direction T. The first and second internal electrodes
11 and 12 are partially disposed opposite to each other with the
ceramic layers 15 therebetween in the thickness direction T. The
first internal electrodes 11 extend to the first end surface 10e.
The first internal electrodes 11 are not exposed in the second end
surface 10f, the first and second main surfaces 10a and 10b, and
the first and second side surfaces 10c and 10d. The second internal
electrodes 12 extend to the second end surface 10f. The second
internal electrodes 12 are not exposed in the first end surface
10e, the first and second main surfaces 10a and 10b, and the first
and second side surfaces 10c and 10d.
The first and second internal electrodes 11 and 12 include opposing
portions disposed opposite to each other in the thickness direction
T and lead portions that are not disposed opposite to each other in
the thickness direction T. The lead portions are connected to the
opposing portions and extend to the first end surface 10e or the
second end surface 10f. In this preferred embodiment, the opposing
portions preferably have the same width as the lead portions in the
width direction W. Accordingly, the first and second internal
electrodes 11 and 12 preferably are substantially rectangular.
The adjacent first internal electrodes 11 may be connected together
in the first end surface 10e. If the adjacent first internal
electrodes 11 are separated in the first end surface 10e, the
distance therebetween is preferably about 7 .mu.m or less, for
example. This allows the regions between the internal electrodes 11
in the first end surface 10e to be reliably plated. Similarly, the
adjacent second internal electrodes 12 may be connected together in
the second end surface 10f. If the adjacent second internal
electrodes 12 are separated in the second end surface 10f, the
distance therebetween is preferably about 7 .mu.m or less, for
example. This allows the regions between the internal electrodes 12
in the second end surface 10f to be reliably plated.
The first and second internal electrodes 11 and 12 preferably each
have a thickness of about 0.3 .mu.m to about 2.0 .mu.m, for
example.
A first external electrode 13 is disposed on the first end surface
10e of the ceramic body 10. The first external electrode 13 is
connected to the first internal electrodes 11. A second external
electrode 14 is disposed on the second end surface 10f of the
ceramic body 10. The second external electrode 14 is connected to
the second internal electrodes 12. While the first and second
external electrodes 13 and 14 preferably are formed only on the
first and second end surfaces 10e and 10f, respectively, in this
preferred embodiment, they may partially cover the main surfaces
10a and 10b and the side surfaces 10c and 10d.
In this preferred embodiment, the first and second external
electrodes 13 and 14 are each formed of a plated layer. The first
and second external electrodes 13 and 14 may further include a
layer stacked on the plated layer on the ceramic body 10.
Alternatively, the first and second external electrodes 13 and 14
may include a plurality of plated layers stacked on top of each
other. The plated layers preferably each have a thickness of about
1 .mu.m to about 15 .mu.m, for example. The first and second
external electrodes 13 and 14 may be formed of, for example, a
metal selected from the group consisting of copper, nickel, silver,
palladium, silver-palladium alloy, gold, tin, lead, bismuth, and
zinc, or an alloy containing the metal. The plated layer(s)
preferably contains no glass component. The plated layer(s)
preferably has a metal content per unit volume of about 99% by
volume or more, for example.
The first and second internal electrodes 11 and 12 and the first
and second external electrodes 13 and 14 may be formed of any
conductive material. The first and second internal electrodes 11
and 12 may be formed of, for example, a metal such as nickel,
copper, silver, palladium, or gold or an alloy containing at least
one such metal. The plated layer(s) for the first and second
external electrodes 13 and 14 may be formed of, for example, a
metal such as copper, nickel, tin, lead, gold, silver, palladium,
bismuth, or zinc or an alloy containing at least one such
metal.
The first and second internal electrodes 11 and 12 and the first
and second external electrodes 13 and 14 are preferably formed of
materials that have good adhesion to each other. For example, if
the first and second internal electrodes 11 and 12 are formed of
nickel or nickel alloy, the first and second external electrodes 13
and 14 are preferably formed of copper or copper alloy plating.
FIG. 4 is a schematic sectional view of a ceramic body before
barrel polishing in this preferred embodiment. FIG. 5 is a
schematic sectional view showing in an enlarged view the portion
enclosed by circle V in FIG. 4. FIG. 6 is a schematic sectional
view showing in an enlarged view the portion enclosed by circle VI
in FIG. 4. FIG. 7 is a schematic sectional view of a ceramic body
after barrel polishing in this preferred embodiment. FIG. 8 is a
schematic sectional view illustrating a plating step in this
preferred embodiment. An example of a method for manufacturing the
ceramic electronic component 1 will now be described in detail,
mainly with reference to FIGS. 4 to 8 as well as FIG. 1.
First, ceramic green sheets for forming the ceramic body 10 are
prepared. The ceramic green sheets can be formed by, for example, a
printing process such as screen printing.
Internal electrode patterns are then printed on the ceramic green
sheets with a conductive paste. The internal electrode patterns are
printed by, for example, screen printing. The paste used for
printing the internal electrode patterns may be a paste containing
conductive particles, an organic binder, and an organic
solvent.
A mother laminate is then formed by stacking a plurality of ceramic
green sheets for forming an outer layer on which no internal
electrode pattern is printed on top of each other, further stacking
the ceramic green sheets on which the internal electrode patterns
are printed, and further stacking a plurality of ceramic green
sheets for forming an outer layer on which no internal electrode
pattern is printed. The mother laminate may be pressed in the
stacking direction by, for example, isostatic pressing.
The green ceramic laminate is then fired to form a ceramic body 30
shown in FIG. 4. The firing temperature may be appropriately set
depending on, for example, the composition of the ceramic laminate.
The firing temperature may be, for example, about 900.degree. C. to
about 1,300.degree. C.
The ceramic green sheets and the internal electrode patterns differ
in shrinkage during firing. In general, the internal electrode
patterns exhibit a higher shrinkage than the ceramic green sheets.
As shown in FIGS. 5 and 6, therefore, the first and second internal
electrodes 11 and 12, formed by firing the internal electrode
patterns, are retracted from the end surfaces 30e and 30f of the
ceramic body 30. In this state, as shown in FIG. 8, media balls 120
used to perform plating of the end surfaces 30e and 30f of the
ceramic body 30 from the first and second internal electrodes 11
and 12 may fail to contact the first and second internal electrodes
11 and 12. Consequently, the first and second external electrodes
13 and 14 may be inappropriately formed because plating does not
grow well from the first and second internal electrodes 11 and
12.
In this preferred embodiment, the ceramic body 30 is processed
before the step of forming the first and second external electrodes
13 and 14 by plating. Specifically, the end surfaces 30e and 30f of
the ceramic body 30 are polished by wet barreling to expose the
first and second internal electrodes 11 and 12. In this way, the
ceramic body 10 shown in FIG. 7 is obtained. Specifically, the
ceramic body 10 is polished to an internal electrode exposure rate
of about 102% to about 153% by wet barrel polishing, for
example.
As used herein, the term "internal electrode exposure rate"
encompasses both the first internal electrode exposure rate and the
second internal electrode exposure rate. The term "first internal
electrode exposure rate" refers to the proportion of the exposure
rate of the lead portions of the first internal electrodes in the
surface to which the first internal electrodes extend to the
exposure rate of the lead portions of the first internal electrodes
in a cross-section of the ceramic body parallel or substantially
parallel to that surface ((exposure rate of lead portions of first
internal electrodes in the surface to which first internal
electrodes extend)/(exposure rate of lead portions of first
internal electrodes in cross-section of ceramic body parallel or
substantially parallel to the surface to which first internal
electrodes extend)). The term "second internal electrode exposure
rate" refers to the proportion of the exposure rate of the lead
portions of the second internal electrodes in the surface to which
the second internal electrodes extend to the exposure rate of the
lead portions of the second internal electrodes in a cross-section
of the ceramic body parallel to that surface ((exposure rate of
lead portions of second internal electrodes in the surface to which
second internal electrodes extend)/(exposure rate of lead portions
of second internal electrodes in cross-section of ceramic body
parallel or substantially parallel to the surface to which second
internal electrodes extend)).
In this preferred embodiment, specifically, the ceramic body 10 is
polished by wet barrel polishing such that the proportion of the
exposure rate of the lead portions of the first internal electrodes
11 in the first end surface 10e, to which the first internal
electrodes 11 extend, to the exposure rate of the lead portions of
the first internal electrodes 11 in a cross-section of the ceramic
body 10 parallel or substantially parallel to the first end surface
10e ((exposure rate of lead portions of first internal electrodes
11 in first end surface 10e to which first internal electrodes 11
extend)/(exposure rate of lead portions of first internal
electrodes 11 in cross-section of ceramic body 10 parallel or
substantially parallel to first end surface 10e)) and the
proportion of the exposure rate of the lead portions of the second
internal electrodes 12 in the second end surface 10f, to which the
second internal electrodes 12 extend, to the exposure rate of the
lead portions of the second internal electrodes 12 in a
cross-section of the ceramic body 10 parallel or substantially
parallel to the second end surface 10f ((exposure rate of lead
portions of second internal electrodes 12 in second end surface 10f
to which second internal electrodes 12 extend)/(exposure rate of
lead portions of second internal electrodes 12 in cross-section of
ceramic body 10 parallel or substantially parallel to second end
surface 10f)) are both about 102% to about 153%, for example.
The ceramic body 10 may be polished by a process other than wet
barrel polishing, such as dry barrel polishing or sand
blasting.
As used herein, the term "internal electrode exposure rate" refers
to the proportion of the exposure rate of the first and second
internal electrodes 11 and 12 in the first and second end surfaces
10e and 10f to the exposure rate of the first and second internal
electrodes 11 and 12 in a cross-section of the ceramic body 10
taken in the width direction W and the thickness direction T
((exposure rate of first and second internal electrodes 11 and 12
in first and second end surfaces 10e and 10f)/(exposure rate of
first and second internal electrodes 11 and 12 in cross-section of
ceramic body 10 taken in width direction W and thickness direction
T)). The internal electrode exposure rate can be measured as
follows. First, energy-dispersive X-ray spectroscopy (EDX) mapping
is performed on the end surfaces 10e and 10f to calculate the
proportion of the content of a particular component in the internal
electrodes 11 and 12 to the content of a particular component in
the ceramic body 10 in the end surfaces 10e and 10f ((content of
particular component in internal electrodes 11 and 12)/(content of
particular component in ceramic body 10)). For example, if the
internal electrodes 11 and 12 mainly contain nickel and the ceramic
body 10 mainly contains titanium or barium, the proportion of the
content of a major component in the internal electrodes 11 and 12
to that of a major component in the ceramic body 10, namely, Ni/Ti
or Ni/Ba, in the end surfaces 10e and 10f is calculated. In the
Examples below, Ni/Ba was calculated.
If the first internal electrodes 11 extend to the first end surface
10e in substantially the same manner that the second internal
electrodes 12 extend to the second end surface 10f, the first and
second internal electrode exposure rates are substantially equal.
Accordingly, if the first internal electrode exposure rate falls
within a predetermined range, the second internal electrode
exposure rate can be assumed to fall within the predetermined
range. Thus, only one of the first and second internal electrode
exposure rates needs to be evaluated.
The end surfaces 10e and 10f of the ceramic body 10 are then
polished to a depth of about 10 .mu.m, for example, to expose a
cross-section. The proportion of the content of a particular
component in the internal electrodes 11 and 12 to the content of a
particular component in the ceramic body 10 ((content of particular
component in internal electrodes 11 and 12)/(content of particular
component in ceramic body 10)) in the cross-section is calculated.
For example, the Ni/Ba in the cross-section is calculated. The
internal electrode exposure rate can be calculated by dividing
((content of particular component in internal electrodes 11 and
12)/(content of particular component in ceramic body 10)) in the
end surfaces 10e and 10f by ((content of particular component in
internal electrodes 11 and 12)/(content of particular component in
ceramic body 10)) in the cross-section. While the end surfaces 10e
and 10f of the ceramic body 10 are polished preferably to a depth
of about 10 .mu.m, for example, in this preferred embodiment, they
do not necessarily have to be polished to a depth of about 10 .mu.m
as long as only the first internal electrodes 11 or the second
internal electrodes 12, rather than both, are exposed in each of
the end surfaces 10e and 10f of the ceramic body 10.
That is, the internal electrode exposure rate is represented as
follows: (((content of particular component in internal electrodes
11 and 12)/(content of particular component in ceramic body 10)) in
end surfaces 10e and 10f)/(((content of particular component in
internal electrodes 11 and 12)/(content of particular component in
ceramic body 10)) in cross-section). For example, if the internal
electrodes 11 and 12 mainly contain nickel and the ceramic body 10
mainly contains barium, the internal electrode exposure rate is
represented as follows: (Ni/Ba in end surfaces 10e and 10f)/(Ni/Ba
in cross-section).
A plating step is then performed to form a plated layer to form the
first and second external electrodes 13 and 14. Specifically, the
plated layer is formed preferably by putting the ceramic body 10
and conductive media balls 20 in a plating bath and stirring the
plating bath.
Because plating is performed on the ceramic body 10, which
preferably has an internal electrode exposure rate of about 102% to
about 153%, in this preferred embodiment, the conductive media
balls 20 reliably contact the internal electrodes 11 and 12, as
shown in FIG. 9. Thus, the plated layer to define the first and
second external electrodes 13 and 14 can be reliably formed.
The plated layer may be formed either by electroplating or by
electroless plating, for example. Preferably, the plated layer is
formed by electroplating because electroless plating requires a
pre-treatment using, for example, a catalyst and therefore tends to
complicate the process of manufacturing the ceramic electronic
component 1.
EXAMPLES
Non-limiting examples of ceramic electronic components having
substantially the same structure as the ceramic electronic
component 1 according to the above preferred embodiment were
fabricated under the following conditions, where 105 samples were
fabricated for each of Examples 1 to 6:
Size of ceramic electronic component: 1.0 mm in length, 0.5 mm in
width, 0.5 mm in height (dimensional tolerance: .+-.0.2 mm)
Material of ceramic body: barium-titanate-based dielectric
ceramic
Internal electrodes: mainly nickel
Thickness of ceramic layers: 0.7 .mu.m
Total number of internal electrodes: 445 layers
Rated voltage: 4.0 V
Capacitance: 10 .mu.F
Barrel Polishing Conditions for Ceramic Body
Process: wet barrel polishing
Number of revolutions: 250 rpm
Media: partially stabilized zirconia (PSZ), 1 mm in diameter, 150
cc
Powder: alumina, 50 cc
Pot volume: 340 cc
Processing time: 0 min (Example 1), 10 min (Example 2), 20 min
(Example 3), 30 min (Example 4), 40 min (Example 5), 50 min
(Example 6)
Plating Conditions
Plating: copper plating about 5 .mu.m thick
Plating bath: pH 8.8, 55.degree. C.
Process: horizontal rotary barrel plating
Number of revolutions: 10 rpm
Conductive media: 1.8 mm in diameter
Current density.times.time: 0.30 A/dm.sup.2.times.150 min
Calculation of Internal Electrode Exposure Rate
The internal electrode exposure rates of Examples 1 to 6 were
calculated as follows, where five samples were taken for
measurement for each of Examples 1 to 6.
(1) The external electrodes were removed from each sample by
electrolytic stripping to expose the end surfaces of the ceramic
body. Subsequently, the Ni/Ba (the proportion of nickel content to
barium content) in the end surfaces of the ceramic body was
determined by EDX mapping.
(2) The end surfaces of the ceramic body after polishing were
polished to a depth of about 10 .mu.m to expose a cross-section in
which the internal electrodes were flush with the ceramic (the
sectional view taken along line A-A in FIG. 7). The Ni/Ba (the
proportion of nickel content to barium content) in the
cross-section was then determined by EDX mapping.
(3) The internal electrode exposure rate was calculated from the
results of Steps (1) and (2) above by the expression (Ni/Ba in end
surface)/(Ni/Ba in cross-section).
(4) The internal electrode exposure rates were calculated through
Steps (1) to (3) in four regions A to D, shown in FIG. 10, having a
size of about 150 .mu.m by about 200 .mu.m (the regions B and C are
located about 20 .mu.m closer to the center in the thickness
direction than the outermost internal electrode, and the regions C
and D are located about 20 .mu.m closer to the center in the width
direction than the ends of the internal electrodes in the width
direction). The results are shown in Table 1 below, where the
internal electrode exposure rate is the average of the internal
electrode exposure rates of the five samples.
The internal electrode exposure rate of a ceramic electronic
component can be measured by removing the external electrodes by
electrolytic stripping to expose the end surfaces of the ceramic
body. For example, if the external electrodes are formed of a
copper plating, as shown in FIG. 11, a cathode 41 and an anode 42,
both formed of a copper plate, are placed in an aqueous copper
sulfate solution 40. A sample 43 for electrolytic stripping is then
placed on the copper plate serving as the anode 42 and is supplied
with current. This causes the copper plating on the sample 43 to
dissolve into the aqueous copper sulfate solution 40. In this way,
the copper plating can be removed.
For each of Examples 1 to 6, 100 samples were evaluated for the
deposition of the external electrodes. Specifically, each sample
was examined for whether or not the plating completely covered the
internal electrodes and the regions therebetween in the surfaces of
the ceramic body. The examples where it was determined that the
plating completely covered the internal electrodes and the regions
therebetween in the surfaces of the ceramic body for every sample
were evaluated as "good," and the examples where it was determined
that the plating incompletely or only partially covered the
internal electrodes and the regions therebetween in the surfaces of
the ceramic body for any sample were evaluated as "poor." The
results are shown in Table 1 below.
The internal electrode exposure rate did not exceed about 153% even
after extended barrel polishing, presumably for the following
reason. The internal electrode exposure rate increases as the
ceramic body is cut by barrel polishing. As the ceramic body is
further cut by barrel polishing, the internal electrodes are also
pressed by the media in the barrel. As a result, the internal
electrodes are extended in the transverse direction so as to cover
the surface of the ceramic body, thus protecting the ceramic body
from being further cut by barrel polishing. Another possible reason
is that the internal electrodes are no longer extended in the
transverse direction by barrel polishing after being extended to a
certain extent.
TABLE-US-00001 TABLE 1 Barrel Average internal electrode exposure
rate (%) polishing Region Region Region Region Deposition Ex. time
(min) A B C D evaluation 1 0 59 55 52 55 Poor 2 10 78 72 73 72 Poor
3 20 112 105 102 102 Good 4 30 132 123 119 120 Good 5 40 153 141
139 139 Good 6 50 151 141 138 141 Good
The results shown in Table 1 demonstrate that external electrodes
can be reliably formed if the internal electrode exposure rate
falls within the range of about 102% to about 153%, for
example.
Second Preferred Embodiment
FIG. 12 is a schematic perspective view of a ceramic electronic
component according to a second preferred embodiment of the present
invention. FIG. 13 is a schematic sectional view, taken in the
length direction L and the thickness direction T, of the ceramic
electronic component according to the second preferred embodiment.
FIG. 14 is a schematic sectional view, taken in the length
direction L and the thickness direction T, of the ceramic
electronic component according to the second preferred
embodiment.
A ceramic electronic component 2 according to this preferred
embodiment includes first internal electrodes 11 and second
internal electrodes 12 that are alternately arranged at intervals
in the width direction W. The first internal electrodes 11 include
opposing portions 11a and lead portions 11b1 and 11b2. The second
internal electrodes 12 include opposing portions 12a and lead
portions 12b1 and 12b2. The opposing portions 11a are disposed
opposite to the opposing portions 12a in the width direction W.
The lead portions 11b1 extend from the opposing portions 11a to the
first main surface 10a. The lead portions 11b2 extend from the
opposing portions 11a to the second main surface 10b.
The first external electrode 13 includes a first electrode portion
13a and a second external electrode portion 13b. The first
electrode portion 13a is disposed on the first main surface 10a.
The first electrode portion 13a is connected to the lead portions
11b1. The second external electrode portion 13b is disposed on the
second main surface 10b. The second external electrode portion 13b
is connected to the lead portions 11b2.
The lead portions 12b1 extend from the opposing portions 12a to the
first main surface 10a. The lead portions 12b2 extend from the
opposing portions 12a to the second main surface 10b.
The second external electrode 14 includes a first electrode portion
14a and a second external electrode portion 14b. The first
electrode portion 14a is disposed on the first main surface 10a.
The first electrode portion 14a is connected to the lead portions
12b1. The second external electrode portion 14b is disposed on the
second main surface 10b. The second external electrode portion 14b
is connected to the lead portions 12b2.
In this preferred embodiment, as in the first preferred embodiment,
the first and second internal electrode exposure rates preferably
are each about 102% to about 153%, for example. Accordingly, the
second preferred embodiment achieves the same advantages as the
first preferred embodiment.
In this preferred embodiment, specifically, the first internal
electrode exposure rate is the proportion of the exposure rate of
the lead portions 11b1 and 11b2 of the first internal electrodes 11
in the first and second main surfaces 10a and 10b, to which the
first internal electrodes 11 extend, to the exposure rate of the
lead portions 11b1 and 11b2 of the first internal electrodes 11 in
a cross-section of the ceramic body 10 parallel or substantially
parallel to the first and second main surfaces 10a and 10b
((exposure rate of lead portions 11b1 and 11b2 of first internal
electrodes 11 in first and second main surfaces 10a and 10b to
which first internal electrodes 11 extend)/(exposure rate of lead
portions 11b1 and 11b2 of first internal electrodes 11 in
cross-section of ceramic body 10 parallel or substantially parallel
to first and second main surfaces 10a and 10b)). The second
internal electrode exposure rate is the proportion of the exposure
rate of the lead portions 12b1 and 12b2 of the second internal
electrodes 12 in the first and second main surfaces 10a and 10b, to
which the second internal electrodes 12 extend, to the exposure
rate of the lead portions 12b1 and 12b2 of the second internal
electrodes 12 in a cross-section of the ceramic body 10 parallel or
substantially parallel to the first and second main surfaces 10a
and 10b ((exposure rate of lead portions 12b1 and 12b2 of second
internal electrodes 12 in first and second main surfaces 10a and
10b to which second internal electrodes 12 extend)/(exposure rate
of lead portions 12b1 and 12b2 of second internal electrodes 12 in
cross-section of ceramic body 10 parallel or substantially parallel
to first and second main surfaces 10a and 10b)).
As shown in this preferred embodiment, the first and second
internal electrodes 11 and 12 may each extend to a plurality of
surfaces of the ceramic body 10. In addition, the first and second
internal electrodes 11 and 12 may extend to the same or different
surfaces.
While preferred embodiments of the present invention have been
described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing from the scope and spirit of the present invention. The
scope of the present invention, therefore, is to be determined
solely by the following claims.
* * * * *